The 1-substituted-2-cyanoimidazole compounds are disclosed in EP-A-298196. Some methods for producing the 1-substituted-2-cyanoimidazole compounds have been proposed therein. However, none of these proposals include the processes of the present invention.
JP-A-4-59766 (The term "JP-A" as used herein means an "unexamined published Japanese patent application") discloses a process for producing 1-hydroxy-2-oxyiminomethylimidazole 3-oxide compounds as an intermediate. However, this process differs from process A of the present invention described below in that substituted glyoxal compounds are used as a starting material.
JP-A-4-59766 discloses a process for producing 2-cyanoimidazole compounds, which comprises reacting a 1-hydroxy-2-oxyiminomethylimidazole 3-oxide compound with a chloride or oxychloride of phosphorus or sulfur. However, JP-A-4-59766 does not disclose process B of the present invention described below producing 2-cyanoimidazole compounds represented by formula.(II) selectively and in a high yield.
EP-A-298196 discloses that (a) isomer mixtures of 1-substituted-2-cyanoimidazole compounds including compounds represented by formulae (I-a) and (I-b) of the present invention can be prepared by sulfamoylating 2-cyanoimidazole compounds represented by formula (II) of the present invention and that (b) the isomer mixtures can be separated by selective hydrolysis. Furthermore, JP-A-4-120063 discloses that only imidazole compounds represented by formula (I-b) of the present invention can be selectively separated from the isomer mixtures by using a solvent and an acid catalyst. However, EP-A-298196 and JP-A-4-120063 do not disclose process C of the present invention described below producing only imidazole compounds represented by formula (I-b) selectively by sulfamoylating and isomerizing the compounds represented by formula (II).
EP-A-298196 proposes some methods for producing 1-substituted-2-cyanoimidazole compounds. However, these methods are not satisfactory in their industrial application. Furthermore, it has been desired to produce 1-substituted-2-cyanoimidazole compounds more economically.
With regard to process A of the present invention, substituted glyoxal compounds used as a starting material in the process for producing 1-hydroxy-2-oxyiminomethylimidazole 3-oxide compounds are disclosed in JP-A-4-59766, but the industrial production of the substituted glyoxal compounds are difficult. JP-B-52-19 (The term "JP-B" as used herein means an "examined Japanese patent publication") discloses a process for producing substituted glyoxal compounds, which comprises reacting ketone and alkyl nitrite gas as starting materials in the presence of hydrogen halide. However, this process comprises a continuous reaction in which .alpha.-oxyimino ketone produced is extracted and removed and thus provides low productivity and requires a special apparatus.
With regard to process B of the present invention, in the process for producing 2-cyanoimidazole compounds disclosed in JP-A-4-59766, the chloride or oxychloride of phosphorus or sulfur for use in the reaction of the process is preferably phosphorus trichloride. When phosphorus oxychloride, phosphorus monochloride, sulfur monochloride, sulfur dichloride, thionyl chloride or sulfuryl chloride is used, the reduction reaction may be incomplete under some conditions. This production process is also disadvantageous in that the use of phosphorus trichloride requires much labor and facilities for the disposal of waste water after reaction. The reaction of phosphorus trichloride is further disadvantageous in that it has an induction period, making it difficult to control the reaction temperature. This preparation process is further disadvantageous in that the resulting compound contains a compound that is not chlorinated in the 4- or 5-position on the imidazole ring. Thus, a separate chlorination step is required to obtain a compound that is chlorinated at the 4- or 5-position on the imidazole ring.
With regard to process C of the present invention, in the process for selectively separating and collecting compounds represented by formula (I-b) from isomer mixtures of 1-substituted-2-cyanoimidazole compounds disclosed in EP-A-298196 and JP-A-4-120063, compounds represented by formula (I-a) are hydrolyzed and the process is thus disadvantageous in that its yield does not exceed the ratio of the isomers of the compounds represented by formula (I-b) and that the post-treatment is complicated.